1. Field Of The Invention
This invention relates in general to devices for positioning objects on water bottoms or seat beds and in particular to a new and useful device for embedding endless pipe into seat bottoms and which includes means for guiding a support member along the pipe as the support member is moved along the bottom by an endless track drive and as a trench is formed behind the support member during its movement.
2. Description Of The Prior Art
Devices for embedding pipes into the sea beds are known in which the supporting structure supports a scraper chain which is located laterally of the pipe to be embedded and it can be lowered by mechanism pivotable about a horizontal axis. The supporting structure also supports a dredge pump provided with a suction snout which either alone or along with the scraper chain digs a trench. On its side opposite to the scraper chain the supporting structure is provided with a bracket carrying two supporting rollers through which the supporting structure bears unilaterally against the water bottom. On the other side the supporting structure bears against the pipe to be embedded through horizontally mounted supporting rollers which may be driven. At both its forward and rear ends considered in the travel direction the supporting structure is equipped with a pair of guide rollers having vertical axes and which apply laterally against the pipe to be embedded. Such a drive through the horizontally mounted supporting rollers is unsatisfactory. It is in no way insured that the friction grip will be sufficient for a trouble free advance of the supporting structure. A determining factor for the friction grip is the weight of the device which must not exceed a certain value which is set by the stress characteristics of the pipe to be embedded. The risk of damaging the pipe to be embedded increases with the total weight of the support structure which is carried by the pipe and the contact rollers which apply laterally against the pipe serve only to effect some stabilization of the device. A device of this nature is described in U.S. Pat. No. 3,590,589.
Another known device for burying pipe lines laid under water which can be lowered onto and moved along the pipe lines to be buried is provided with a mechanism for cutting a trench in the form of one or more jet openings for hydraulic lines. The hydraulic cutting mechanisms are located on both sides of the pipe to be embedded and carried by a supporting structure which is provided with pontoon skids on each side of the pipe to be embedded and extend along the axis of the latter and are equipped with abrasion sheathing at their undersides. The forward ends of the pontoon skids are connected to the bow of a vessel by means of traction ropes by which the supporting structure is towed over the sea bottom. In addition the supporting structure is provided with horizontally and vertically mounted guide rollers which apply against the pipe to be embedded. The device is advanced exclusively by a tugboat. Therefore neither a uniform nor a sure advance is provided since the motion of the boat depends on the surface streams and the wind. The towed device is exposed to uncontrollable varying tension stresses and this may lead to damaging of the device. The difficulties described above are particularly acute when the device is used in deep areas of the sea.
Another known device for embedding pipes in the sea beds includes a cutting mechanism which comprises two internal suction cutter heads which are mounted on a supporting structure laterally of the pipe to be embedded and are adapted to be lowered and swung inwardly. The suction conduit ends approximately in the middle zone of the cutting heads and these cutting heads are equipped with spiral shaped cutting blades. The cutting heads are operated hydraulically. The suction lines lead to a suction pump which is mounted on the vessel. The supporting structure of the suction heads bears against the pipe to be embedded through supporting rollers having inclined axes extending in a plane perpendicular to the travel direction. The supporting rollers are driven. A disadvantage of this device is that the total weight of the device must be absorbed by the pipe to be embedded. The mounting of the dredge pump on the vessel and the provision of a relatively long suction line is disadvantageous. In addition there is no possibility of stabilizing the digging device. Such a device is described in U.S. Pat. No. 3,429,132.
There are also known devices of this kind in which the supporting structure for a trenching mechanism is supported by two endless track drive gears which can be advanced under water bottoms on each side of the pipe to be embedded. Two bracket arms joined in the space between the drive gears and carrying the drive for the cutting tools on their ends are pivoted to the drive gears. The cutting tools comprise cutting and suction heads and the drive axes are inclined so that below the pipe the suction and heads are closely adjacent to each other. In addition the suction and cutting heads are pivotally supported about axes extending in the travel direction so that the cutting mechanism can be removed from the trench to be cut both by swinging the bracket arms and by lateral swinging of the heads. Two swinging motions are necessary in order to effect this. In addition the drive is provided with a device permitting the control of the depth of the trench to be cut as a function of the diameter of the pipe to be embedded. For this purpose laterally inclined rollers are mounted on the swing arms which apply against the pipe to be embedded. A horizontal guide roller is further provided which is carried by a support to which the automatically controlled lateral rollers are pivotally connected. Due to the use of two endless track drive gears the device is very expensive. This is especially true if pipes having a larger diameter are to be embedded. The design of the device results in a heavy weight which is again a disadvantage as the device has to be supported by the pipe to be embedded. Such a device is described in U.S. Pat. No. 3,583,170.